Neurotrophins and their receptors in nerve injury and repair

A Comparative Investigation of Axon-Blood Vessel Growth Interaction in the Regenerating Sciatic and Optic Nerves in Adult Mice

The vascular and the nervous systems share similarities in addition to their complex role in providing oxygen and nutrients to all cells. Both are highly branched networks that frequently grow close to one another during development. Vascular patterning and neural wiring share families of guidance cues and receptors. Most recently, this relationship has been investigated in terms of peripheral nervous system (PNS) regeneration, where nerves and blood vessels often run in parallel so endothelial cells guide the formation of the Büngner bands which support axonal regeneration. Here, we characterized the vascular response in regenerative models of the central and peripheral nervous system. After sciatic nerve crush, followed by axon regeneration, there was a significant increase in the blood vessel density 7 days after injury. In addition, the optic nerve crush model was used to evaluate intrinsic regenerative potential activated with a combined treatment that stimulated retinal ganglion cells (RGCs) regrowth. We observed that a 2-fold change in the total number of blood vessels occurred 7 days after optic nerve crush compared to the uncrushed nerve. The difference increased up to a 2.7-fold change 2 weeks after the crush. Interestingly, we did not observe differences in the total number of blood vessels 2 weeks after crush, compared to animals that had received combined treatment for regeneration and controls. Therefore, the vascular characterization showed that the increase in vascular density was not related to the efficiency of both peripheral and central axonal regeneration.

The influence of tag sequence on recombinant humanized collagen (rhCol) and the evaluation of rhCol on Schwann cell behaviors

Recombinant humanized collagen (rhCol) was an extracellular matrix (ECM)-inspired biomimetic biomaterial prepared by biosynthesis technology, which was considered non-allergenic and could possibly activate tissue regeneration. The influence of tag sequence on both structures and performances of rhCol type III (rhCol III) was investigated, and the effect of rhCol III on cell behaviors was evaluated and discussed using Schwann cells (SCs) as in vitro model that was critical in the repair process after peripheral nerve injury. The results demonstrated that the introduction of tag sequence would influence both advanced structures and properties of rhCol III, while rhCol III regulated SCs adhesion, spreading, migration and proliferation. Also, both nerve growth factor and brain-derived neurotrophic factor increased when exposed to rhCol III. As the downstream proteins of integrin-mediated cell adhesions, phosphorylation of focal adhesion kinase and expression of vinculin was up-regulated along with the promotion of SCs adhesion and migration. The current findings contributed to a better knowledge of the interactions between rhCol III and SCs, and further offered a theoretical and experimental foundation for the development of rhCol III-based medical devices and clinical management of peripheral nerve injury.

Effectiveness of exercise interventions in animal models of multiple sclerosis

Multiple sclerosis (MS) is associated with an impaired immune system that severely affects the spinal cord and brain, and which is marked by progressive inflammatory demyelination. Patients with MS may benefit from exercise training as a suggested course of treatment. The most commonly used animal models of studies on MS are experimental autoimmune/allergic encephalomyelitis (EAE) models. The present review intends to concisely discuss the interventions using EAE models to understand the effectiveness of exercise as treatment for MS patients and thereby provide clear perspective for future research and MS management. For the present literature review, relevant published articles on EAE animal models that reported the impacts of exercise on MS, were extracted from various databases. Existing literature support the concept that an exercise regimen can reduce the severity of some of the clinical manifestations of EAE, including neurological signs, motor function, pain, and cognitive deficits. Further results demonstrate the mechanisms of EAE suppression with information relating to the immune system, demyelination, regeneration, and exercise in EAE. The role for neurotrophic factors has also been investigated. Analyzing the existing reports, this literature review infers that EAE is a suitable animal model that can help researchers develop further understanding and treatments for MS. Besides, findings from previous animal studies supports the contention that exercise assists in ameliorating MS progression.

Neurotrophic factors in the porcine ovary: Their effects on follicular growth, oocyte maturation, and developmental competence

Pigs are cost-effective industrial animals because they produce a large number of offspring and have shorter rebreeding intervals compared with other animals, such as non-human primates. The reproductive physiology of pigs has been studied over the past several decades. However, there is not enough research on the effects of the neurotrophic factors on the ovarian physiology and development in pigs. As the ovary is a highly innervated organ, various neurotrophic factors during ovarian development can promote the growth of nerve fibers and improve the development of ovarian cells. Thus, investigating the role of neurotrophic factors on ovarian development, and the relationship between neurotrophic factors and porcine female reproduction is worth studying. In this review, we focused on the physiological roles of various neurotrophic factors in porcine ovaries and summarized the current status of the studies related to the relationship between neurotrophic factors and porcine ovarian development.

Brain-Derived Neurotropic Factor in Neurodegenerative Disorders

Globally, neurodegenerative diseases cause a significant degree of disability and distress. Brain-derived neurotrophic factor (BDNF), primarily found in the brain, has a substantial role in the development and maintenance of various nerve roles and is associated with the family of neurotrophins, including neuronal growth factor (NGF), neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5). BDNF has affinity with tropomyosin receptor kinase B (TrKB), which is found in the brain in large amounts and is expressed in several cells. Several studies have shown that decrease in BDNF causes an imbalance in neuronal functioning and survival. Moreover, BDNF has several important roles, such as improving synaptic plasticity and contributing to long-lasting memory formation. BDNF has been linked to the pathology of the most common neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease. This review aims to describe recent efforts to understand the connection between the level of BDNF and neurodegenerative diseases. Several studies have shown that a high level of BDNF is associated with a lower risk for developing a neurodegenerative disease.

A review of dementia, focusing on the distinct roles of viral protein corona and MMP9 in dementia: Potential pharmacotherapeutic priorities

Dementia, in particular, is a defining feature of Alzheimer's and Parkinson's diseases. Because of the combination of motor and cognitive impairments, Parkinson's disease dementia (PDD) has a greater impact on affected people than Alzheimer's disease dementia (ADD) and others. If one family member develops dementia, the other members will suffer greatly in terms of social and occupational functioning. Currently, no relevant treatment is available based on an examination of the absolute pathophysiology of dementia. As a result, our objective of current review encouraged to look for dementia pharmacotherapy based on their pathogenesis. We systematically searched electronic databases such as PubMed, Scopus, and ESCI for information on the pathophysiology of demetia, as well as their treatment with allopathic and herbal medications. By modulating intermediate proteins, oxidative stress, viral protein corona, and MMP9 are etiological factors that cause dementia. The pathophysiology of ADD was described by two hypotheses: the amyloid cascade hypothesis and the tau and tangle hypothesis. ADD is caused by an increase in amyloid-beta (Aβ) and neurofibrillary tangles in the cerebrum. The viral protein corona (VPC) is more contagious and helps to form amyloid-beta (Aβ) plaques and neurofibrillary tangles in the cerebrum. Thioredoxin interacting protein (TXNIP) inside the BBB encourages Aβ to become more engaged. PDD is caused by decreased or absent dopamine secretion from nerve cells in the substantia nigra, as well as PRKN gene deletion/duplication mutations, and shift in the PRKN-PACRG organisation, all of which are linked to ageing. This article discussed the pathophysiology of dementia, as well as a list of herbal medications that can easily cross the BBB and have a therapeutic effect on dementia.

The basic science of optic nerve regeneration

Diverse insults to the optic nerve result in partial to total vision loss as the axons of retinal ganglion cells are destroyed. In glaucoma, axons are injured at the optic nerve head; in other optic neuropathies, axons can be damaged along the entire visual pathway. In all cases, as mammals cannot regenerate injured central nervous system cells, once the axons are lost, vision loss is irreversible. However, much has been learned about how retinal ganglion cells respond to axon injuries, and many of these crucial discoveries offer hope for future regenerative therapies. Here we review the current understanding regarding the temporal progression of axonal degeneration. We summarize known survival and regenerative mechanisms in mammals, including specific signaling pathways, key transcription factors, and reprogramming genes. We cover mechanisms intrinsic to retinal ganglion cells as well as their interactions with myeloid and glial cell populations in the retina and optic nerve that affect survival and regeneration. Finally, we highlight some non-mammalian species that are able to regenerate their retinal ganglion cell axons after injury, as understanding these successful regenerative responses may be essential to the rational design of future clinical interventions to regrow the optic nerve. In the end, a combination of many different molecular and cellular interventions will likely be the only way to achieve functional recovery of vision and restore quality of life to millions of patients around the world.

Initial serum GM-CSF levels are associated with the severity of cerebral small vessel disease in microscopic polyangiitis patients

Serum cytokine levels were comprehensively measured, and the association with cerebrovascular lesions on brain magnetic resonance imaging (MRI) in microscopic polyangiitis (MPA) patients was investigated. The initial serum granulocyte-macrophage colony-stimulating factor (GM-CSF) levels were significantly higher in the high-grade white matter hyperintensities (WMH) group than those in the low-grade WMH group. In multivariate analyses, high serum levels of GM-CSF were independently associated with high-grade WMH. The initial serum GM-CSF levels correlated positively with the Birmingham Vasculitis Activity Score and semi-quantitative scales of WMH. The initial serum GM-CSF levels were associated with the severity of WMH in MPA patients.

Small molecule modulation of the p75 neurotrophin receptor suppresses age- and genotype-associated neurodegeneration in HIV gp120 transgenic mice

The persistence of HIV in the central nervous system leads to cognitive deficits in up to 50% of people living with HIV even with systemic suppression by antiretroviral treatment. The interaction of chronic inflammation with age-associated degeneration places these individuals at increased risk of accelerated aging and other neurodegenerative diseases and no treatments are available that effectively halt these processes. The adverse effects of aging and inflammation may be mediated, in part, by an increase in the expression of the p75 neurotrophin receptor (p75^NTR) which shifts the balance of neurotrophin signaling toward less protective pathways. To determine if modulation of p75^NTR could modify the disease process, we treated HIV gp120 transgenic mice with a small molecule ligand designed to engage p75^NTR and downregulate degenerative signaling. Daily treatment with 50 mg/kg LM11A-31 for 4 months suppressed age- and genotype-dependent activation of microglia, increased microtubule associated protein-2 (MAP-2), reduced dendritic varicosities and slowed the loss of parvalbumin immunoreactive neurons in the hippocampus. An age related accumulation of microtubule associated protein Tau was identified in the hippocampus in extracellular clusters that co-expressed p75^NTR suggesting a link between Tau and p75^NTR. Although the significance of the relationship between p75^NTR and Tau is unclear, a decrease in Tau-1 immunoreactivity as gp120 mice entered old age (>16 months) suggests that the Tau may transition to more pathological modifications; a process blocked by LM11A-31. Overall, the effects of LM11A-31 are consistent with strong neuroprotective and anti-inflammatory actions that have significant therapeutic potential.

Cadaver Nerve Grafts: Past, Present and Future

Nerve grafts represent an invaluable tool, when reconstructing nerve defects of more than 1 cm. Historically, the criterion standard use of autografts has relied on the premise of using nonessential sensory nerves to fulfill the principle of replacing "like with like," while simultaneously minimizing the infliction of undue morbidity on the patient. The reconstructive surgeon thus faces a dilemma when extensive nerve damage requires reconstruction, or when donor nerves are not available or limited such as in the pediatric population. Cadaver nerve grafts (CNG) uniquely allow for reconstruction of large nerve lesions without the presence of host morbidity. The following article reviews the use of CNG, its indications, advantages, and disadvantages, as well as provides some case studies of real-world application. In addition, an insight into the future perspectives of CNG is provided.

Nerve growth factor activates autophagy in Schwann cells to enhance myelin debris clearance and to expedite nerve regeneration

Rationale: Autophagy in Schwann cells (SCs) is crucial for myelin debris degradation and clearance following peripheral nerve injury (PNI). Nerve growth factor (NGF) plays an important role in reconstructing peripheral nerve fibers and promoting axonal regeneration. However, it remains unclear if NGF effect in enhancing nerve regeneration is mediated through autophagic clearance of myelin debris in SCs.

Methods: In vivo, free NGF solution plus with/without pharmacological inhibitors were administered to a rat sciatic nerve crush injury model. In vitro, the primary Schwann cells (SCs) and its cell line were cultured in normal medium containing NGF, their capable of swallowing or clearing degenerated myelin was evaluated through supplement of homogenized myelin fractions.

Results: Administration of exogenous NGF could activate autophagy in dedifferentiated SCs, accelerate myelin debris clearance and phagocytosis, as well as promote axon and myelin regeneration at early stage of PNI. These NGF effects were effectively blocked by autophagy inhibitors. In addition, inhibition of the p75 kD neurotrophin receptor (p75^NTR) signal or inactivation of the AMP-activated protein kinase (AMPK) also inhibited the NGF effect as well.

Conclusions: NGF effect on promoting early nerve regeneration is closely associated with its accelerating autophagic clearance of myelin debris in SCs, which probably regulated by the p75^NTR/AMPK/mTOR axis. Our studies thus provide strong support that NGF may serve as a powerful pharmacological therapy for peripheral nerve injuries.

Decreased cpg15 augments oxidative stress in sleep deprived mouse brain

Sleep deprivation (SD) has detrimental effects on the physiological function of the brain. However, the underlying mechanism remains elusive. In the present study, we investigated the expression of candidate plasticity-related gene 15 (cpg15), a neurotrophic gene, and its potential role in SD using a REM-SD mouse model. Immunofluorescent and Western blot analysis revealed that the expression of cpg15 protein decreased in the hippocampus, ventral group of the dorsal thalamus (VENT), and somatosensory area of cerebral cortex (SSP) after 24-72 h of REM-SD, and the oxidative stress in these brain regions was increased in parallel, as indicated by the ratio of glutathione (GSH) to its oxidative product (GSSG). Over-expression of cpg15 in thalamus, hippocampus, and cerebral cortex mediated by AAV reduced the oxidative stress in these regions, indicating that the decrease of cpg15 might be a cause that augments oxidative stress in the sleep deprived mouse brain. Collectively, the results imply that cpg15 may play a protective function in the SD-subjected mouse brain via an anti-oxidative function. To our knowledge, this is the first time to provide evidences in the role of cpg15 against SD-induced oxidative stress in the brain.

Octadecaneuropeptide (ODN) Induces N2a Cells Differentiation through a PKA/PLC/PKC/MEK/ERK-Dependent Pathway: Incidence on Peroxisome, Mitochondria, and Lipid Profiles

Neurodegenerative diseases are characterized by oxidative stress, mitochondrial damage, and death of neuronal cells. To counteract such damage and to favor neurogenesis, neurotrophic factors could be used as therapeutic agents. Octadecaneuropeptide (ODN), produced by astrocytes, is a potent neuroprotective agent. In N2a cells, we studied the ability of ODN to promote neuronal differentiation. This parameter was evaluated by phase contrast microscopy, staining with crystal violet, cresyl blue, and Sulforhodamine 101. The effect of ODN on cell viability and mitochondrial activity was determined with fluorescein diacetate and DiOC₆(3), respectively. The impact of ODN on the topography of mitochondria and peroxisomes, two tightly connected organelles involved in nerve cell functions and lipid metabolism, was evaluated by transmission electron microscopy and fluorescence microscopy: detection of mitochondria with MitoTracker Red, and peroxisome with an antibody directed against the ABCD3 peroxisomal transporter. The profiles in fatty acids, cholesterol, and cholesterol precursors were determined by gas chromatography, in some cases coupled with mass spectrometry. Treatment of N2a cells with ODN (10^-14 M, 48 h) induces neurite outgrowth. ODN-induced neuronal differentiation was associated with modification of topographical distribution of mitochondria and peroxisomes throughout the neurites and did not affect cell viability and mitochondrial activity. The inhibition of ODN-induced N2a differentiation with H89, U73122, chelerythrine and U0126 supports the activation of a PKA/PLC/PKC/MEK/ERK-dependent signaling pathway. Although there is no difference in fatty acid profile between control and ODN-treated cells, the level of cholesterol and some of its precursors (lanosterol, desmosterol, lathosterol) was increased in ODN-treated cells. The ability of ODN to induce neuronal differentiation without cytotoxicity reinforces the interest for this neuropeptide with neurotrophic properties to overcome nerve cell damage in major neurodegenerative diseases.

Adipose-Derived Mesenchymal Stem Cells Applied in Fibrin Glue Stimulate Peripheral Nerve Regeneration

Mesenchymal stem cells (MSCs) hold a great promise for cell therapy. To date, they represent one of the best choices for the treatment of post-traumatic injuries of the peripheral nervous system. Although autologous can be easily transplanted in the injured area, clinical advances in this filed have been impaired by lack of preservation of graft cells into the injury area after transplantation. Indeed, cell viability is not retained after injection into the blood stream, and cells injected directly into the area of injury either are washed off or inhibit regeneration through scar formation and neuroma development. This study proposes a new way of MSCs delivery to the area of traumatic injury by using fibrin glue, which not only fixes cells at the site of application but also provides extracellular matrix support. Using a sciatic nerve injury model, MSC derived from adipose tissue embedded in fibrin glue were able to enter the nerve and migrate mainly retrogradely after transplantation. They also demonstrated a neuroprotective effect on DRG L5 sensory neurons and stimulated axon growth and myelination. Post-traumatic changes of the sensory neuron phenotype were also improved. Importantly, MSCs stimulated nerve angiogenesis and motor function recovery. Therefore, our data suggest that MSC therapy using fibrin glue is a safe and efficient method of cell transplantation in cases of sciatic nerve injury, and that this method of delivery of regeneration stimulants could be beneficial for the successful treatment of other central and peripheral nervous system conditions.

Induction of Neuronal Differentiation of Murine N2a Cells by Two Polyphenols Present in the Mediterranean Diet Mimicking Neurotrophins Activities: Resveratrol and Apigenin

In the prevention of neurodegeneration associated with aging and neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease), neuronal differentiation is of interest. In this context, neurotrophic factors are a family of peptides capable of promoting the growth, survival, and/or differentiation of both developing and immature neurons. In contrast to these peptidyl compounds, polyphenols are not degraded in the intestinal tract and are able to cross the blood–brain barrier. Consequently, they could potentially be used as therapeutic agents in neurodegenerative pathologies associated with neuronal loss, thus requiring the stimulation of neurogenesis. We therefore studied the ability to induce neuronal differentiation of two major polyphenols present in the Mediterranean diet: resveratrol (RSV), a major compound found in grapes and red wine, and apigenin (API), present in parsley, rosemary, olive oil, and honey. The effects of these compounds (RSV and API: 6.25–50 µM) were studied on murine neuro-2a (N2a) cells after 48 h of treatment without or with 10% fetal bovine serum (FBS). Retinoic acid (RA: 6.25–50 µM) was used as positive control. Neuronal differentiation was morphologically evaluated through the presence of dendrites and axons. Cell growth was determined by cell counting and cell viability by staining with fluorescein diacetate (FDA). Neuronal differentiation was more efficient in the absence of serum than with 10% FBS or 10% delipidized FBS. At concentrations inducing neuronal differentiation, no or slight cytotoxicity was observed with RSV and API, whereas RA was cytotoxic. Without FBS, RSV and API, as well as RA, trigger the neuronal differentiation of N2a cells via signaling pathways simultaneously involving protein kinase A (PKA)/phospholipase C (PLC)/protein kinase C (PKC) and MEK/ERK. With 10% FBS, RSV and RA induce neuronal differentiation via PLC/PKC and PKA/PLC/PKC, respectively. With 10% FBS, PKA and PLC/PKC as well as MEK/ERK signaling pathways were not activated in API-induced neuronal differentiation. In addition, the differentiating effects of RSV and API were not inhibited by cyclo[DLeu⁵] OP, an antagonist of octadecaneuropeptide (ODN) which is a neurotrophic factor. Moreover, RSV and API do not stimulate the expression of the diazepam-binding inhibitor (DBI), the precursor of ODN. Thus, RSV and API are able to induce neuronal differentiation, ODN and its receptor are not involved in this process, and the activation of the (PLC/PKC) signaling pathway is required, except with apigenin in the presence of 10% FBS. These data show that RSV and API are able to induce neuronal differentiation and therefore mimic neurotrophin activity. Thus, RSV and API could be of interest in regenerative medicine to favor neurogenesis.

Bioactivity-Guided Isolation of Neuritogenic Factor from the Seeds of the Gac Plant (Momordica cochinchinensis)

Nerve growth factor (NGF) is an endogenously produced protein with the capacity to induce central nervous system (CNS) neuronal differentiation and repair. NGF signaling involves its binding to tropomyosin-related kinase (Trk) receptors, internalization, and initiation of phosphorylation cascades which cause microtubule reorganization and neuronal outgrowth. Because NGF cannot cross the blood-brain barrier, its therapeutic use is limited. Synthetic peptides that can act as NGF receptor agonists (NGF mimetics) are known to attenuate neurodegenerative pathologies in experimental models of Alzheimer's disease and Parkinson's disease; however, the existence of plant-based NGF mimetics is uncertain. For this reason, we recently completed a high throughput screening of over 1100 nutraceuticals (vitamins, herbal plant parts, polyphenolics, teas, fruits, and vegetables) to identify neuritogenic factor using a PC-12 cell model. Remarkably we found only one, commonly known as the seed of Gac plant (Momordica cochinchinensis) (MCS). In the current study, we further investigated this seed for its neuritogenic effect using bioactivity-guided chemical separations. The data show no biological neuritogenic activity in any chemical solvent fraction, where activity was exclusive to the crude protein. MSC crude proteins were then separated by 1D electrophoresis, where the active neuritogenic activity was confirmed to have a molecular mass of approximately 17 kDa. Subsequently, the 17kDa band was excised, digested, and run on a UPLC-MS/MS with a Q Exactive Hybrid Quadrupole-Orbitrap Mass Spectrometer with data evaluated diverse tools such as X! Tandem, OMS, and K-score algorithms. Proteomic evaluation of the 17kDa band confirmed evidence for 11S globulin subunit beta, napin, oleosin, Momordica trypsin inhibitors (TI) MCoTI-I /II, and many isoforms of Two Inhibitor Peptide Topologies (TIPTOPs). While all peptides identified correspond to the genus/species, Momordica cochinchinensis and Cucumis Sativus, a significant limitation of the analysis is the nonexistence of full annotation for the Momordica cochinchinensis proteome. In conclusion, these findings demonstrate that there is a stable protein within MCS having a mass of 17kDa with the capacity to induce neurite outgrowth. Future work will be required to establish the therapeutic value of the MCS for the treatment of neurodegenerative diseases.

BDNF: A Key Factor with Multipotent Impact on Brain Signaling and Synaptic Plasticity

Brain-derived neurotrophic factor (BDNF) is one of the most widely distributed and extensively studied neurotrophins in the mammalian brain. Among its prominent functions, one can mention control of neuronal and glial development, neuroprotection, and modulation of both short- and long-lasting synaptic interactions, which are critical for cognition and memory. A wide spectrum of processes are controlled by BDNF, and the sometimes contradictory effects of its action can be explained based on its specific pattern of synthesis, comprising several intermediate biologically active isoforms that bind to different types of receptor, triggering several signaling pathways. The functions of BDNF must be discussed in close relation to the stage of brain development, the different cellular components of nervous tissue, as well as the molecular mechanisms of signal transduction activated under physiological and pathological conditions. In this review, we briefly summarize the current state of knowledge regarding the impact of BDNF on regulation of neurophysiological processes. The importance of BDNF for future studies aimed at disclosing mechanisms of activation of signaling pathways, neuro- and gliogenesis, as well as synaptic plasticity is highlighted.

Systematic assessment of surface functionality on nanoscale patterns for topographic contact guidance of cells

The ability of surface topography to influence cellular response has been widely accepted, leading the way towards the development of potential neural prosthetics.

The neurotrophic effects of different human dental mesenchymal stem cells

The current gold standard treatment for peripheral nerve injury is nerve grafting but this has disadvantages such as donor site morbidity. New techniques focus on replacing these grafts with nerve conduits enhanced with growth factors and/or various cell types such as mesenchymal stem cells (MSCs). Dental-MSCs (D-MSCs) including stem cells obtained from apical papilla (SCAP), dental pulp stem cells (DPSC), and periodontal ligament stem cells (PDLSC) are potential sources of MSCs for nerve repair. Here we present the characterization of various D-MSCs from the same human donors for peripheral nerve regeneration. SCAP, DPSC and PDLSC expressed BDNF, GDNF, NGF, NTF3, ANGPT1 and VEGFA growth factor transcripts. Conditioned media from D-MSCs enhanced neurite outgrowth in an in vitro assay. Application of neutralizing antibodies showed that brain derived neurotrophic factor plays an important mechanistic role by which the D-MSCs stimulate neurite outgrowth. SCAP, DPSC and PDLSC were used to treat a 10 mm nerve gap defect in a rat sciatic nerve injury model. All the stem cell types significantly enhanced axon regeneration after two weeks and showed neuroprotective effects on the dorsal root ganglia neurons. Overall the results suggested SCAP to be the optimal dental stem cell type for peripheral nerve repair.

Neural Stem Cells, Neural Progenitors, and Neurotrophic Factors

Neural stem cells (NSCs) have been proposed as a promising cellular source for the treatment of diseases in nervous systems. NSCs can self-renew and generate major cell types of the mammalian central nervous system throughout adulthood. NSCs exist not only in the embryo, but also in the adult brain neurogenic region: the subventricular zone (SVZ) of the lateral ventricle. Embryonic stem (ES) cells acquire NSC identity with a default mechanism. Under the regulations of leukemia inhibitory factor (LIF) and fibroblast growth factors, the NSCs then become neural progenitors. Neurotrophic and differentiation factors that regulate gene expression for controlling neural cell fate and function determine the differentiation of neural progenitors in the developing mammalian brain. For clinical application of NSCs in neurodegenerative disorders and damaged neurons, there are several critical problems that remain to be resolved: 1) how to obtain enough NSCs from reliable sources for autologous transplantation; 2) how to regulate neural plasticity of different adult stem cells; 3) how to control differentiation of NSCs in the adult nervous system. In order to understand the mechanisms that control NSC differentiation and behavior, we review the ontogeny of NSCs and other stem cell plasticity of neuronal differentiation. The role of NSCs and their regulation by neurotrophic factors in CNS development are also reviewed.

Early gene activation initiates neuroinflammation prior to VSV neuroinvasion: Impact on antiviral responses and sleep

Rapid eye movement (REM) sleep is rapidly and persistently suppressed during vesicular stomatitis virus (VSV) encephalitis in C57Bl/6J (B6) mice. REM sleep suppression was associated with a complex global brain chemokine/cytokine response with bimodal kinetics although regionally distinct cytokine profiles were readily identified. Cytokine mRNA was translated either immediately or suppressed until the pathogen was cleared from the CNS. Innate signaling pathway (TLRs, RIG-I) activation occurred rapidly and sequentially prior to VSV neuroinvasion suggesting that antiviral states are quickly established in the CNS in advance of viral pathogen penetration. Il1β suppressed REM sleep mimicking aspects of VSV-induced sleep alterations whereas some robustly induced chemokines may be protective of REM. Thus, multiple brain chemokines may mediate sleep across VSV encephalitis via differential somnogenic effects.

MPP+-Lesioned Mice: an Experimental Model of Motor, Emotional, Memory/Learning, and Striatal Neurochemical Dysfunctions

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces motor and nonmotor dysfunctions resembling Parkinson's disease (PD); however, studies investigating the effects of 1-methyl-4-phenylpyridinium (MPP⁺), an active oxidative product of MPTP, are scarce. This study investigated the behavioral and striatal neurochemical changes (related to oxidative damage, glial markers, and neurotrophic factors) 24 h after intracerebroventricular administration of MPP⁺ (1.8-18 μg/mouse) in C57BL6 mice. MPP⁺ administration at high dose (18 μg/mouse) altered motor parameters, since it increased the latency to leave the first quadrant and reduced crossing, rearing, and grooming responses in the open-field test and decreased rotarod latency time. MPP⁺ administration at low dose (1.8 μg/mouse) caused specific nonmotor dysfunctions as it produced a depressive-like effect in the forced swim test and tail suspension test, loss of motivational and self-care behavior in the splash test, anxiety-like effect in the elevated plus maze test, and short-term memory deficit in the step-down inhibitory avoidance task, without altering ambulation. MPP⁺ at doses of 1.8-18 μg/mouse increased tyrosine hydroxylase (TH) immunocontent and at 18 μg/mouse increased α-synuclein and decreased parkin immunocontent. The astrocytic calcium-binding protein S100B and glial fibrillary acidic protein (GFAP)/S100B ratio was decreased following MPP⁺ administration (18 μg/mouse). At this highest dose, MPP⁺ increased the ionized calcium-binding adapter molecule 1 (Iba-1) immunocontent, suggesting microglial activation. Also, MPP⁺ at a dose of 18 μg/mouse increased thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) levels and increased glutathione peroxidase (GPx) and hemeoxygenase-1 (HO-1) immunocontent, suggesting a significant role for oxidative stress in the MPP⁺-induced striatal damage. MPP⁺ (18 μg/mouse) also increased striatal fibroblast growth factor 2 (FGF-2) and brain-derived neurotrophic factor (BDNF) levels. Moreover, MPP⁺ decreased tropomyosin receptor kinase B (TrkB) immunocontent. Finally, MPP⁺ (1.8-18 μg/mouse) increased serum corticosterone levels and did not alter acetylcholinesterase (AChE) activity in the striatum but increased it in cerebral cortex and hippocampus. Collectively, these results indicate that MPP⁺ administration at low doses may be used as a model of emotional and memory/learning behavioral deficit related to PD and that MPP⁺ administration at high dose could be useful for analysis of striatal dysfunctions associated with motor deficits in PD.

Effects of age and insulin-like growth factor-1 on rat neurotrophin receptor expression after nerve injury

INTRODUCTION

Neurotrophin receptors, such as p75(NTR) , direct neuronal response to injury. Insulin-like growth factor-1 receptor (IGF-1R) mediates the increase in p75(NTR) during aging. The aim of this study was to examine the effect of aging and insulin-like growth factor-1 (IGF-1) treatment on recovery after peripheral nerve injury.

METHODS

Young and aged rats underwent tibial nerve transection with either local saline or IGF-1 treatment. Neurotrophin receptor mRNA and protein expression were quantified.

RESULTS

Aged rats expressed elevated baseline IGF-1R (34% higher, P = 0.01) and p75(NTR) (68% higher, P < 0.01) compared with young rats. Post-injury, aged animals expressed significantly higher p75(NTR) levels (68.5% above baseline at 4 weeks). IGF-1 treatment suppressed p75(NTR) gene expression at 4 weeks (17.2% above baseline, P = 0.002) post-injury.

CONCLUSIONS

Local IGF-1 treatment reverses age-related declines in recovery after peripheral nerve injuries by suppressing p75(NTR) upregulation and pro-apoptotic complexes. IGF-1 may be considered a viable adjuvant therapy to current treatment modalities. Muscle Nerve 54: 769-775, 2016.

Dynamic self-guiding analysis of Alzheimer's disease

We applied a self-guiding evolutionary algorithm to initiate the synthesis of the Alzheimer's disease-related data and literature. A protein interaction network associated with amyloid-beta precursor protein (APP) and a seed model that treats Alzheimer's disease as progressive dysregulation of APP-associated signaling were used as dynamic “guides” and structural “filters” in the recursive search, analysis, and assimilation of data to drive the evolution of the seed model in size, detail, and complexity. Analysis of data and literature across sub-disciplines and system-scale discovery platforms suggests a key role of dynamic cytoskeletal connectivity in the stability, plasticity, and performance of multicellular networks and architectures. Chronic impairment and/or dysregulation of cell adhesions/synapses, cytoskeletal networks, and/or reversible epithelial-to-mesenchymal-like transitions, which enable and mediate the stable and coherent yet dynamic and reconfigurable multicellular architectures, may lead to the emergence and persistence of the disordered, wound-like pockets/microenvironments of chronically disconnected cells. Such wound-like microenvironments support and are supported by pro-inflammatory, pro-secretion, de-differentiated cellular phenotypes with altered metabolism and signaling. The co-evolution of wound-like microenvironments and their inhabitants may lead to the selection and stabilization of degenerated cellular phenotypes, via acquisition of epigenetic modifications and mutations, which eventually result in degenerative disorders such as cancer and Alzheimer's disease.

Pathway-focused PCR array profiling of enriched populations of laser capture microdissected hippocampal cells after traumatic brain injury

Cognitive deficits in survivors of traumatic brain injury (TBI) are associated with irreversible neurodegeneration in brain regions such as the hippocampus. Comparative gene expression analysis of dying and surviving neurons could provide insight into potential therapeutic targets. We used two pathway-specific PCR arrays (RT2 Profiler Apoptosis and Neurotrophins & Receptors PCR arrays) to identify and validate TBI-induced gene expression in dying (Fluoro-Jade-positive) or surviving (Fluoro-Jade- negative) pyramidal neurons obtained by laser capture microdissection (LCM). In the Apoptosis PCR array, dying neurons showed significant increases in expression of genes associated with cell death, inflammation, and endoplasmic reticulum (ER) stress compared with adjacent, surviving neurons. Pro-survival genes with pleiotropic functions were also significantly increased in dying neurons compared to surviving neurons, suggesting that even irreversibly injured neurons are able to mount a protective response. In the Neurotrophins & Receptors PCR array, which consists of genes that are normally expected to be expressed in both groups of hippocampal neurons, only a few genes were expressed at significantly different levels between dying and surviving neurons. Immunohistochemical analysis of selected, differentially expressed proteins supported the gene expression data. This is the first demonstration of pathway-focused PCR array profiling of identified populations of dying and surviving neurons in the brain after TBI. Combining precise laser microdissection of identifiable cells with pathway-focused PCR array analysis is a practical, low-cost alternative to microarrays that provided insight into neuroprotective signals that could be therapeutically targeted to ameliorate TBI-induced neurodegeneration.

Differentiation of endogenous neural stem cells in adult versus neonatal rats after brachial plexus root avulsion injury

An experimental model of brachial plexus root avulsion injury of cervical dorsal C_5-6 was established in adult and neonatal rats. Real-time PCR showed that the levels of brain-derived neurotrophic factor, nerve growth factor and neurotrophin-3 in adult rats increased rapidly 1 day after brachial plexus root avulsion injury, and then gradually decreased to normal levels by 21 days. In neonatal rats, levels of the three neurotrophic factors were decreased on the first day after injury, and then gradually increased from the seventh day and remained at high levels for an extended period of time. We observed that greater neural plasticity contributed to better functional recovery in neonatal rats after brachial plexus root avulsion injury compared with adult rats. Moreover, immunohistochemical staining showed that the number of bromodeoxyuridine/nestin-positive cells increased significantly in the spinal cords of the adult rats compared with neonatal rats after brachial plexus root avulsion injury. In addition, the number of bromodeoxyuridine/glial fibrillary acidic protein-positive cells in adult rats was significantly higher than in neonatal rats 14 and 35 days after brachial plexus injury. Bromodeoxyuridine/β-tubulin-positive cells were not found in either adult or neonatal rats. These results indicate that neural stem cells differentiate mainly into astrocytes after brachial plexus root avulsion injury. Furthermore, the degree of neural stem cell differentiation in neonatal rats was lower than in adult rats.

NGF in Early Embryogenesis, Differentiation, and Pathology in the Nervous and Immune Systems

The physiology of NGF is extremely complex, and although the study of this neurotrophin began more than 60 years ago, it is far from being concluded. NGF, its precursor molecule pro-NGF, and their different receptor systems (i.e., TrkA, p75NTR, and sortilin) have key roles in the development and adult physiology of both the nervous and immune systems. Although the NGF receptor system and the pathways activated are similar for all types of cells sensitive to NGF, the effects exerted during embryonic differentiation and in committed mature cells are strikingly different and sometimes opposite. Bearing in mind the pleiotropic effects of NGF, alterations in its expression and synthesis, as well as variations in the types of receptor available and in their respective levels of expression, may have profound effects and play multiple roles in the development and progression of several diseases. In recent years, the use of NGF or of inhibitors of its receptors has been prospected as a therapeutic tool in a variety of neurological diseases and injuries. In this review, we outline the different roles played by the NGF system in various moments of nervous and immune system differentiation and physiology, from embryonic development to aging. The data collected over the past decades indicate that NGF activities are highly integrated among systems and are necessary for the maintenance of homeostasis. Further, more integrated and multidisciplinary studies should take into consideration these multiple and interactive aspects of NGF physiology in order to design new therapeutic strategies based on the manipulation of NGF and its intracellular pathways.

Relationship between growth factors and its implication in the pathogenesis of leprosy

Leprosy is a chronic infectious disease caused by Mycobacterium leprae which affects the skin and peripheral nervous system. The immune response of the host determines the clinical course of the disease. The tuberculoid form is the result of high cell-mediated immunity characterized by a Th1 response, whereas the lepromatous form is characterized by low cell-mediated immunity and a Th2 humoral response. The neural damage established produces marked changes in the expression of growth factors such as nerve growth factor (NGF) and its receptors (NGF-R). The expression of NGF, associated with the expression of Th1 and Th2 cytokines, might be involved in the tissue damage caused by the bacillus. Therefore, the objective of this study was to correlate the immunoexpression patterns of NGF and NGF-R in the different clinical forms of leprosy, and to associate the findings with the in situ expression of TGF-β and clinical classification of the disease. TGF-β, NGF and NGF-R immunoexpression was analyzed by immunohistochemistry in paraffin-embedded material. Most patients were males with a mean age of 40.7 years. TGF-β levels were significantly higher in the lepromatous forms. No significant difference in the immunoexpression of NGF or NGF-R was observed between the clinical forms, but expression tended to be higher at the lepromatous pole. There was a significant positive correlation between NGF and NGF-R in the different clinical forms of leprosy. A significant positive correlation was observed between NGF, NGF-R and TGF-β. It can be concluded that, even existing evidence on the role of these molecules in the clinical spectrum of leprosy.

Cortical reorganization after spinal cord injury: always for good?

Plasticity constitutes the basis of behavioral changes as a result of experience. It refers to neural network shaping and re-shaping at the global level and to synaptic contacts remodeling at the local level, either during learning or memory encoding, or as a result of acute or chronic pathological conditions. 'Plastic' brain reorganization after central nervous system lesions has a pivotal role in the recovery and rehabilitation of sensory and motor dysfunction, but can also be "maladaptive". Moreover, it is clear that brain reorganization is not a "static" phenomenon but rather a very dynamic process. Spinal cord injury immediately initiates a change in brain state and starts cortical reorganization. In the long term, the impact of injury - with or without accompanying therapy - on the brain is a complex balance between supraspinal reorganization and spinal recovery. The degree of cortical reorganization after spinal cord injury is highly variable, and can range from no reorganization (i.e. "silencing") to massive cortical remapping. This variability critically depends on the species, the age of the animal when the injury occurs, the time after the injury has occurred, and the behavioral activity and possible therapy regimes after the injury. We will briefly discuss these dependencies, trying to highlight their translational value. Overall, it is not only necessary to better understand how the brain can reorganize after injury with or without therapy, it is also necessary to clarify when and why brain reorganization can be either "good" or "bad" in terms of its clinical consequences. This information is critical in order to develop and optimize cost-effective therapies to maximize functional recovery while minimizing maladaptive states after spinal cord injury.

Trophic factors in the pathogenesis and therapy for retinal degenerative diseases

Trophic factors are endogenously secreted proteins that act in an autocrine and/or paracrine fashion to affect vital cellular processes such as proliferation, differentiation, and regeneration, thereby maintaining overall cell homeostasis. In the eye, the major contributors of these molecules are the retinal pigment epithelial (RPE) and Müller cells. The primary paracrine targets of these secreted proteins include the photoreceptors and choriocapillaris. Retinal degenerative diseases such as age-related macular degeneration and retinitis pigmentosa are characterized by aberrant function and/or eventual death of RPE cells, photoreceptors, choriocapillaris, and other retinal cells. We discuss results of in vitro and in vivo animal studies in which candidate trophic factors, either singly or in combination, were used in an attempt to ameliorate photoreceptor and/or retinal degeneration. We also examine current trophic factor therapies as they relate to the treatment of retinal degenerative diseases in clinical studies.

Neurotrophin 3 transduction augments remyelinating and immunomodulatory capacity of neural stem cells

Neural stem cells (NSCs) have therapeutic potential in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS); however, to date, their use has resulted in only limited clinical and pathological improvement. To enhance their therapeutic capacity, in the present study, we transduced bone marrow-derived NSCs (BM-NSCs) with neurotrophin 3 (NT-3), a potent neurotrophic factor that is both neuroprotective and immunomodulatory. We found that BM-NSCs transduced with NT-3 reduced central nervous system (CNS) inflammation and neurological deficits in ongoing EAE significantly more than conventional NSC therapy, and, in addition, had the following advantages: (i) enhanced BM-NSC proliferation and differentiation into oligodendrocytes and neurons, as well as inhibited differentiation into astrocytes, thus promoting remyelination and neuronal repopulation, and reducing astrogliosis; (ii) enhanced anti-inflammatory capacity of BM-NSCs, thus more effectively suppressing CNS inflammation and accelerating remyelination; (iii) the easy accessibility of BM-NSCs provides another advantage over brain-derived NSCs for MS therapy; and (iv) a novel Tet-on system we used enables efficient control of NT-3 expression. Thus, our study provides a novel approach to break the vicious inflammation-demyelination cycle, and could pave the way to an easily accessible and highly effective therapy for CNS inflammatory demyelination.

High-frequency stimulation of the globus pallidus interna nucleus modulates GFRα1 gene expression in the basal ganglia

Deep brain stimulation (DBS) is an established therapy for movement disorders such as Parkinson's disease (PD). Although the efficacy of DBS is clear, its precise molecular mechanism remains unknown. The glial cell line derived factor (GDNF) family of ligands has been shown to confer neuroprotective effects on dopaminergic neurons, and putaminal infusion of GDNF have been investigated in PD patients with promising results. Despite the potential therapeutic role of GDNF in alleviating motor symptoms, there is no data on the effects of electrical stimulation on GDNF-family receptor (GFR) expression in the basal ganglia structures. Here, we report the effects of electrical stimulation on GFRα1 isoforms, particularly GFRα1a and GFRα1b. Wistar rats underwent 2 hours of high frequency stimulation (HFS) at the globus pallidus interna nucleus. A control group was subjected to a similar procedure but without stimulation. The HFS group, sacrificed 24 hours after treatment, had a threefold decrease in mRNA expression level of GFRα1b (p=0.037), but the expression level reverted to normal 72 hours after stimulation. Our preliminary data reveal the acute effects of HFS on splice isoforms of GFRα1, and suggest that HFS may modulate the splice isoforms of GFRα1a and GFRα1b to varying degrees. Going forward, elucidating the interactions between HFS and GFR may shed new insights into the complexity of GDNF signaling in the nervous system and lead to better design of clinical trials using these signaling pathways to halt disease progression in PD and other neurodegenerative diseases.

The Effects of Antecedent Exercise on Motor Function Recovery and Brain-derived Neurotrophic Factor Expression after Focal Cerebral Ischemia in Rats

[Purpose] In the present study, we investigated the effect of antecedent exercise on functional recovery and brain-derived neurotrophic factor (BDNF) expression following focal cerebral ischemia injury. [Subjects] The rat middle cerebral artery occlusion (MCAO) model was employed. Adult male Sprague-Dawley rats were randomly divided into 4 groups. Group I included untreated normal rats (n=10); Group II included untreated rats with focal cerebral ischemia (n=10); Group III included rats that performed treadmill exercise (20 m/min) training after focal cerebral ischemia (n=10); and Group IV included rats that performed antecedent treadmill exercise (20 m/min) training before focal cerebral ischemia (n=10) as well as treadmill exercise after ischemia. At different time points (1, 7, 14, and 21 days) Garcia’s score, and the hippocampal expressions level of BDNF were examined. [Results] In the antecedent exercise group, improvements in the motor behavior index (Garcia’s score) were observed and hippocampal BDNF protein expression levels increased. [Conclusion] These results indicate that antecedent treadmill exercise, before permanent brain ischemia exerts a neuroprotective effect against ischemia brain injury by improving motor performance and increasing the level of BDNF expression. Furthermore, the antecedent treadmill exercise of appropriate intensity is critical for post-stroke rehabilitation.

Oligodendroglia and neurotrophic factors in neurodegeneration

Myelination by oligodendroglial cells (OLs) enables the propagation of action potentials along neuronal axons, which is essential for rapid information flow in the central nervous system. Besides saltatory conduction, the myelin sheath also protects axons against inflammatory and oxidative insults. Loss of myelin results in axonal damage and ultimately neuronal loss in demyelinating disorders. However, accumulating evidence indicates that OLs also provide support to neurons via mechanisms beyond the insulating function of myelin. More importantly, an increasing volume of reports indicates defects of OLs in numerous neurodegenerative diseases, sometimes even preceding neuronal loss in pre-symptomatic episodes, suggesting that OL pathology may be an important mechanism contributing to the initiation and/or progression of neurodegeneration. This review focuses on the emerging picture of neuronal support by OLs in the pathogenesis of neurodegenerative disorders through diverse molecular and cellular mechanisms, including direct neuron-myelin interaction, metabolic support by OLs, and neurotrophic factors produced by and/or acting on OLs.

Glaucoma and optic nerve repair

Glaucoma is a leading cause of irreversible blindness worldwide and causes progressive visual impairment attributable to the dysfunction and death of retinal ganglion cells (RGCs). Progression of visual field damage is slow and typically painless. Thus, glaucoma is often diagnosed after a substantial percentage of RGCs has been damaged. To date, clinical interventions are mainly restricted to the reduction of intraocular pressure (IOP), one of the major risk factors for this disease. However, the lowering of IOP is often insufficient to halt or reverse the progress of visual loss, underlining the need for the development of alternative treatment strategies. Several lines of evidence suggest that axonal damage of RGCs occurs primary at the optic nerve head, where axons appear to be most vulnerable. Axonal injury leads to the functional loss of RGCs and subsequently induces the death of the neurons. However, the detailed molecular mechanism(s) underlying IOP-induced optic nerve injury remain poorly understood. Moreover, whether glaucoma pathophysiology is primarily axonal, glial, or vascular remains unclear. Therefore, protective strategies to prevent further axonal and subsequent soma degeneration are of great importance to limit the progression of sight loss. In addition, strategies that stimulate injured RGCs to regenerate and reconnect axons with their central targets are necessary for functional restoration. The present review provides an overview of the context of glaucoma pathogenesis and surveys recent findings regarding potential strategies for axonal regeneration of RGCs and optic nerve repair, focusing on the role of cytokines and their downstream signaling pathways.

Effects of acute selective pudendal nerve electrical stimulation after simulated childbirth injury

During childbirth, a combinatorial injury occurs and can result in stress urinary incontinence (SUI). Simulated childbirth injury, consisting of vaginal distension (VD) and pudendal nerve crush (PNC), results in slowed recovery of continence, as well as decreased expression of brain-derived neurotrophic factor (BDNF), a regenerative cytokine. Electrical stimulation has been shown to upregulate BDNF in motor neurons and facilitate axon regrowth through the increase of β(II)-tubulin expression after injury. In this study, female rats underwent selective pudendal nerve motor branch (PNMB) stimulation after simulated childbirth injury or sham injury to determine whether such stimulation affects bladder and anal function after injury and whether the stimulation increases BDNF expression in Onuf's nucleus after injury. Rats received 4 h of VD followed by bilateral PNC and 1 h of subthreshold electrical stimulation of the left PNMB and sham stimulation of the right PNMB. Rats underwent filling cystometry and anal pressure recording before, during, and after the stimulation. Bladder and anal contractile function were partially disrupted after injury. PNMB stimulation temporarily inhibited bladder contraction after injury. Two days and 1 wk after injury, BDNF expression in Onuf's nucleus of the stimulated side was significantly increased compared with the sham-stimulated side, whereas β(II)-tubulin expression in Onuf's nucleus of the stimulated side was significantly increased only 1 wk after injury. Acute electrical stimulation of the pudendal nerve proximal to the crush site upregulates BDNF and β(II)-tubulin in Onuf's nucleus after simulated childbirth injury, which could be a potential preventive option for SUI after childbirth injury.

ω-3 fatty acid eicosapentaenoic acid attenuates MPP+-induced neurodegeneration in fully differentiated human SH-SY5Y and primary mesencephalic cells

Eicosapentaenoic acid (EPA), a neuroactive omega-3 fatty acid, has been demonstrated to exert neuroprotective effects in experimental models of Parkinson's disease (PD), but the cellular mechanisms of protection are unknown. Here, we studied the effects of EPA in fully differentiated human SH-SY5Y cells and primary mesencephalic neurons treated with MPP(+) . In both in-vitro models of PD, EPA attenuated an MPP(+) -induced reduction in cell viability. EPA also prevented the presence of electron-dense cytoplasmic inclusions in SH-SY5Y cells. Then, possible mechanisms of the neuroprotection were studied. In primary neurons, EPA attenuated an MPP(+) -induced increase in Tyrosine-related kinase B (TrkB) receptors. In SH-SY5Y cells, EPA down-regulated reactive oxygen species and nitric oxide. This antioxidant effect of EPA may have been mediated by its inhibition of neuronal NADPH oxidase and cyclo-oxygenase-2 (COX-2), as MPP(+) increased the expression of these enzymes. Furthermore, EPA prevented an increase in cytosolic phospholipase A2 (cPLA2), an enzyme linked with COX-2 in the potentially pro-inflammatory arachidonic acid cascade. Lastly, EPA attenuated an increase in the bax:bcl-2 ratio, and cytochrome c release. However, EPA did not prevent mitochondrial enlargement or a decrease in mitochondrial membrane potential. This study demonstrated cellular mechanisms by which EPA provided neuroprotective effects in experimental PD.

Brain-derived neurotrophic factor and the course of experimental cerebral malaria

The role of neurotrophic factors on the integrity of the central nervous system (CNS) during cerebral malaria (CM) infection remains obscure, but the long-standing neurocognitive sequelae often observed in rescued children can be attributed in part to the modulation of neuronal survival and synaptic plasticity. To discriminate the contribution of key responses in the time-sequence of the pathogenic events that trigger the development of neurocognitive malaria syndrome we defined four stages (I-IV) of the neurological progression of CM in C57BL/6 mice infected with Plasmodium berghei ANKA. Upregulation of ICAM-1, VCAM-1, e-selectin and p-selectin expression was detected in all cerebral regions before parasitized red blood cells (pRBC) accumulation. As the severity of symptoms increased, BDNF mRNA progressively diminished in several brain regions, earliest in the thalamus-hypothalamus, cerebellum, brainstem and cortex, and correlated with a four-stage disease sequence. Immunohistochemical confocal microscopy revealed changes in the BDNF distribution pattern, suggesting altered axonal transport. During CM progression, molecular markers of neurological infection and inflammation in the parasite and the host, respectively, were accompanied by a switch in the brain constitutive proteasome to the immunoproteasome, which could impede normal protein turnover. In parallel with BDNF downregulation, NCAM expression also diminished with increased CM severity. Together, these data suggest that changes in BDNF availability could be involved in the pathogenesis of CM.

Double gene therapy with granulocyte colony-stimulating factor and vascular endothelial growth factor acts synergistically to improve nerve regeneration and functional outcome after sciatic nerve injury in mice

Peripheral-nerve injuries are a common clinical problem and often result in long-term functional deficits. Reconstruction of peripheral-nerve defects is currently undertaken with nerve autografts. However, there is a limited availability of nerves that can be sacrificed and the functional recovery is never 100% satisfactory. We have previously shown that gene therapy with vascular endothelial growth factor (VEGF) significantly improved nerve regeneration, neuronal survival, and muscle activity. Our hypothesis is that granulocyte colony-stimulating factor (G-CSF) synergizes with VEGF to improve the functional outcome after sciatic nerve transection. The left sciatic nerves and the adjacent muscle groups of adult mice were exposed, and 50 or 100 μg (in 50 μl PBS) of VEGF and/or G-CSF genes was injected locally, just below the sciatic nerve, and transferred by electroporation. The sciatic nerves were transected and placed in an empty polycaprolactone (PCL) nerve guide, leaving a 3-mm gap to challenge nerve regeneration. After 6 weeks, the mice were perfused and the sciatic nerve, the dorsal root ganglion (DRG), the spinal cord and the gastrocnemius muscle were processed for light and transmission electron microscopy. Treated animals showed significant improvement in functional and histological analyses compared with the control group. However, the best results were obtained with the G-CSF+VEGF-treated animals: quantitative analysis of regenerated nerves showed a significant increase in the number of myelinated fibers and blood vessels, and the number of neurons in the DRG and motoneurons in the spinal cord was significantly higher. Motor function also showed that functional recovery occurred earlier in animals receiving G-CSF+VEGF-treatment. The gastrocnemius muscle showed an increase in weight and in the levels of creatine phosphokinase, suggesting an improvement of reinnervation and muscle activity. These results suggest that these two factors acted synergistically and optimized the nerve repair potential, improving regeneration after a transection lesion.

Hemodialysis decreases serum brain-derived neurotrophic factor concentration in humans

In the present study we have evaluated the effect of a single hemodialysis session on the brain-derived neurotrophic factor levels in plasma [BDNF](pl) and in serum [BDNF](s) as well as on the plasma isoprostanes concentration [F(2) isoprostanes](pl), plasma total antioxidant capacity (TAC) and plasma cortisol levels in chronic kidney disease patients. Twenty male patients (age 69.8 ± 2.9 years (mean ± SE)) with end-stage renal disease undergoing maintenance hemodialysis on regular dialysis treatment for 15-71 months participated in this study. A single hemodialysis session, lasting 4.2 ± 0.1 h, resulted in a decrease (P = 0.014) in [BDNF](s) by ~42 % (2,574 ± 322 vs. 1,492 ± 327 pg ml(-1)). This was accompanied by an increase (P < 10(-4)) of [F(2)-Isoprostanes](pl) (38 ± 3 vs. 116 ± 16 pg ml(-1)), decrease (P < 10(-4)) in TAC (1,483 ± 41 vs. 983 ± 35 trolox equivalents, μmol l(-1)) and a decrease (P = 0.004) in plasma cortisol level (449.5 ± 101.2 vs. 315.3 ± 196.3 nmol l(-1)). No changes (P > 0.05) in [BDNF](pl) and the platelets count were observed after a single dialysis session. Furthermore, basal [BDNF](s) in the chronic kidney disease patients was significantly lower (P = 0.03) when compared to the age-matched control group (n = 23). We have concluded that the observed decrease in serum BDNF level after hemodialysis accompanied by elevated [F(2)-Isoprostanes](pl) and decreased plasma TAC might be caused by enhanced oxidative stress induced by hemodialysis.

Mesenchymal stem cells in a polycaprolactone conduit promote sciatic nerve regeneration and sensory neuron survival after nerve injury

Despite the fact that the peripheral nervous system is able to regenerate after traumatic injury, the functional outcomes following damage are limited and poor. Bone marrow mesenchymal stem cells (MSCs) are multipotent cells that have been used in studies of peripheral nerve regeneration and have yielded promising results. The aim of this study was to evaluate sciatic nerve regeneration and neuronal survival in mice after nerve transection followed by MSC treatment into a polycaprolactone (PCL) nerve guide. The left sciatic nerve of C57BL/6 mice was transected and the nerve stumps were placed into a biodegradable PCL tube leaving a 3-mm gap between them; the tube was filled with MSCs obtained from GFP+ animals (MSC-treated group) or with a culture medium (Dulbecco's modified Eagle's medium group). Motor function was analyzed according to the sciatic functional index (SFI). After 6 weeks, animals were euthanized, and the regenerated sciatic nerve, the dorsal root ganglion (DRG), the spinal cord, and the gastrocnemius muscle were collected and processed for light and electron microscopy. A quantitative analysis of regenerated nerves showed a significant increase in the number of myelinated fibers in the group that received, within the nerve guide, stem cells. The number of neurons in the DRG was significantly higher in the MSC-treated group, while there was no difference in the number of motor neurons in the spinal cord. We also found higher values of trophic factors expression in MSC-treated groups, especially a nerve growth factor. The SFI revealed a significant improvement in the MSC-treated group. The gastrocnemius muscle showed an increase in weight and in the levels of creatine phosphokinase enzyme, suggesting an improvement of reinnervation and activity in animals that received MSCs. Immunohistochemistry documented that some GFP+ -transplanted cells assumed a Schwann-cell-like phenotype, as evidenced by their expression of the S-100 protein, a Schwann cell marker. Our findings suggest that using a PCL tube filled with MSCs is a good strategy to improve nerve regeneration after a nerve transection in mice.

Promoting optic nerve regeneration

Vision is the most important sense for humans and it is irreversibly impaired by axonal damage of retinal ganglion cells (RGCs) in the optic nerve due to the lack of axonal regeneration. The failure of regeneration is partially attributable to factors located in the inhibitory environment of the forming glial scar and myelin as well as an insufficient intrinsic ability for axonal regrowth. Moreover, RGCs undergo apoptotic cell death after optic nerve injury, eliminating any chance for regeneration. In this review, we discuss the different aspects that cause regenerative failure in the optic nerve. Moreover, we describe discoveries of the last two decades demonstrating that under certain circumstances mature RGCs can be transformed into an active regenerative state allowing these neurons to survive axotomy and to regenerate axons in the injured optic nerve. In this context we focus on the role of the cytokines ciliary neutrophic factor (CNTF) and leukemia inhibitory factor (LIF), their receptors and the downstream signaling pathways. Furthermore, we discuss strategies to overcome inhibitory signaling induced by molecules associated with optic nerve myelin and the glial scar as well as the regenerative outcome after combinatorial treatments. These findings are encouraging and may open the possibility that clinically meaningful regeneration may become achievable one day in the future.

Plasma concentrations but not serum concentrations of brain-derived neurotrophic factor are related to pro-inflammatory cytokines in patients undergoing major abdominal surgery

OBJECTIVES

To investigate peripheral brain-derived neurotrophic factor (BDNF) concentrations in the perioperative period, their relationship with transforming growth factor-β1 (TGF-β1 tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-6 genetics.

DESIGN AND METHODS

Prospective, observational study. BDNF, TGF-β1, IL-6 and TNF-α were analysed at baseline (T0), 5 h (T1), 24 h (T2) and 5 days (T3) after surgery, in 21 patients. The IL-6 -174 G/C polymorphism was genotyped.

RESULTS

Serum BDNF concentrations decreased (P=0.048), correlated with TGF-β1 (r=0.610 at T1, r=0.493 at T2, r=0.554 at T3). Plasma BDNF concentrations raised (P=0.049), correlated with IL-6 and TNF-α at T1 (r=0.495 and r=0.441, respectively). BDNF response was predictable from TNF-α and IL-6 concentrations and the IL-6 -174 G/C genotype.

CONCLUSION

Serum and plasma BDNF concentrations could relate to platelet activation and inflammatory response, respectively. IL-6 genetics played a role in the BDNF acute response.

Nerve growth factor-immobilized electrically conducting fibrous scaffolds for potential use in neural engineering applications

Engineered scaffolds simultaneously exhibiting multiple cues are highly desirable for neural tissue regeneration. To this end, we developed a neural tissue engineering scaffold that displays submicrometer-scale features, electrical conductivity, and neurotrophic activity. Specifically, electrospun poly(lactic acid-co-glycolic acid) (PLGA) nanofibers were layered with a nanometer thick coating of electrically conducting polypyrrole (PPy) presenting carboxylic groups. Then, nerve growth factor (NGF) was chemically immobilized onto the surface of the fibers. These NGF-immobilized PPy-coated PLGA (NGF-PPyPLGA) fibers supported PC12 neurite formation ( 28.0±3.0% of the cells) and neurite outgrowth (14.2 μm median length), which were comparable to that observed with NGF (50 ng/mL) in culture medium ( 29.0±1.3%, 14.4 μm). Electrical stimulation of PC12 cells on NGF-immobilized PPyPLGA fiber scaffolds was found to further improve neurite development and neurite length by 18% and 17%, respectively, compared to unstimulated cells on the NGF-immobilized fibers. Hence, submicrometer-scale fibrous scaffolds that incorporate neurotrophic and electroconducting activities may serve as promising neural tissue engineering scaffolds such as nerve guidance conduits.

Exercise and disease progression in multiple sclerosis: can exercise slow down the progression of multiple sclerosis?

It has been suggested that exercise (or physical activity) might have the potential to have an impact on multiple sclerosis (MS) pathology and thereby slow down the disease process in MS patients. The objective of this literature review was to identify the literature linking physical exercise (or activity) and MS disease progression. A systematic literature search was conducted in the following databases: PubMed, SweMed+, Embase, Cochrane Library, PEDro, SPORTDiscus and ISI Web of Science. Different methodological approaches to the problem have been applied including (1) longitudinal exercise studies evaluating the effects on clinical outcome measures, (2) cross-sectional studies evaluating the relationship between fitness status and MRI findings, (3) cross-sectional and longitudinal studies evaluating the relationship between exercise/physical activity and disability/relapse rate and, finally, (4) longitudinal exercise studies applying the experimental autoimmune encephalomyelitis (EAE) animal model of MS. Data from intervention studies evaluating disease progression by clinical measures (1) do not support a disease-modifying effect of exercise; however, MRI data (2), patient-reported data (3) and data from the EAE model (4) indicate a possible disease-modifying effect of exercise, but the strength of the evidence limits definite conclusions. It was concluded that some evidence supports the possibility of a disease-modifying potential of exercise (or physical activity) in MS patients, but future studies using better methodologies are needed to confirm this.